Reduced brittleness of multi-walled carbon nanotubes (MWCNTs) containing Al 2 O 3 -C refractories with boron carbide

Microstructure, properties, and application of low carbon Al2O3‐C refractories used as submerged entry nozzles

“…However, SiC phase detected in the XRD pattern at 1200°C was not clearly observed in the matrix by SEM, which might be located inside the network of carbon fibers. 18 Higher temperature allowed the formation of high contents of SiO and Si vapors, 9,18 and (1) SiO (g) + 2C (fibers) = SiC w (s) + CO (g) thus SiC whiskers with longer lengths were produced with rising temperature to 1400°C, as displayed in Figure 4D,E. These whiskers had high length/diameter ratios (≥100, 5 ~ 10 μm in length and 40 ~ 60 nm in diameter) and became entangled with each other.…”

“…3,30 It is known from the literature that the amorphous carbon fibers also can enhance the thermal shock resistance of carbon containing refractories by "pulling out" mechanism. 9,11 This is because the interlocking network of the nanoscaled phases plays an active role in crack bridging and deflection during crack propagation. As a result, the residual strength ratio of this refractory was decreased to 42.52%.…”

“…SiC whiskers started to emerge at 1200°C ( Figure 4B,C), in accordance with the XRD result, mainly owing to the increased Si-containing vapors. 9,18 These whiskers were thinner (~20 nm in diameter) and shorter (~500 nm in length) but larger in quantity compared with the sample TAC, by which a more dense and entangled network was developed. 22 As already reported in the literature, 11,20,[23][24][25] the introduction of nano carbons into Al 2 O 3 -C refractories can help to develop whiskers.…”

“…5 Despite the above advantages, a major drawback regarding the use of Al 2 O 3 -C refractories is the carbon pick-up in the steel flow during casting. The application of nano carbons in the form of nano-carbon black (CB), multiple-wall carbon nanotubes (MWCNTs), carbon nanofibers (CNFs), etc, has increasingly attracted attention because of its great potential in developing low carbon containing refractories with enhanced properties, 8,9 but the poor dispersion and the high cost limit its further applications in industrial scale. Therefore, it is of great importance to develop low carbon containing Al 2 O 3 -C refractories, especially when the steel industry moves toward clean steel technology and low carbon economy.…”

“…7 However, the decrease in carbon content usually leads to a dramatic reduction of the resistance to both thermal shock and slag corrosion. The application of nano carbons in the form of nano-carbon black (CB), multiple-wall carbon nanotubes (MWCNTs), carbon nanofibers (CNFs), etc, has increasingly attracted attention because of its great potential in developing low carbon containing refractories with enhanced properties, 8,9 but the poor dispersion and the high cost limit its further applications in industrial scale. 10 The in situ formation of nano carbon fibers and/or nano ceramic whiskers was found to have similar advantages as those obtained by the direct incorporation of nanoscale additives.…”